Flow and coral morphology control coral surface pH: implications for the effects of ocean acidification

Chan, Neil C.S., Wangpraseurt, Daniel, Kuhl, Michael, and Connolly, Sean R. (2016) Flow and coral morphology control coral surface pH: implications for the effects of ocean acidification. Frontiers in Marine Science, 26. pp. 637-641.

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Abstract

The future impact of ocean acidification (OA) on corals is disputed in part because mathematical models used to predict these impacts do not seem to capture, or offer a framework to adequately explain, the substantial variability in acidification effects observed in empirical studies. The build-up of a diffusive boundary layer (DBL), wherein solute transport is controlled by diffusion, can lead to pronounced differences between the bulk seawater pH, and the actual pH experienced by the organism, a factor rarely considered in mathematical modeling of ocean acidification effects on corals. In the present study, we developed a simple diffusion-reaction-uptake model that was experimentally parameterized based on direct microsensor measurements of coral tissue pH and O2 within the DBL of a branching and a massive coral. The model accurately predicts tissue surface pH for different coral morphologies and under different flow velocities as a function of ambient pH. We show that, for all cases, tissue surface pH is elevated at lower flows, and thus thicker DBLs. The relative effects of OA on coral surface pH was controlled by flow and we show that under low flow velocities tissue surface pH under OA conditions (pHSWS = 7.8) can be equal to the pH under normal conditions (pHSWS = 8.2). We conclude that OA effects on corals in nature will be complex as the degree to which they are controlled by flow appears to be species specific.

Item ID: 47812
Item Type: Article (Research - C1)
ISSN: 2296-7745
Keywords: climate change; carbonate chemistry; calcification; diffusive boundary layer
Additional Information:

Copyright © 2016 Chan, Wangpraseurt, Kühl and Connolly. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Funders: Australian Research Council (ARC), James Cook University (JCU), Danish Council for Independent Research/Natural Sciences, The Plant Functional Biology and Climate Change Cluster, University of Technology, Sydney (UTS)
Date Deposited: 15 Mar 2017 04:50
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060203 Ecological Physiology @ 40%
06 BIOLOGICAL SCIENCES > 0699 Other Biological Sciences > 069902 Global Change Biology @ 60%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 100%
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